Large sized rear projection screen

ABSTRACT

A rear projection screen does not block the image light and provides a perfect complete image. The screen includes a Fresnel lens, and a cylindrical lens array consisting of a plurality of cylindrical lens elements. These elements are independent from each other and in parallel, and arranged closely between adjacent cylindrical lens element, so that there are no luminous flux loss therebetween. A strengthening area, which is provided with a rigid reinforced member connecting with cylindrical lens elements on two sides thereof, is formed on the are a being from their contact portion to the image-light exist-side surface between adjacent cylindrical lens elements. An ambient light absorbing portion is formed at the image-light exit side in the strengthening area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage application of internationalapplication number PCT/CN00/00338 filed on Oct. 18, 2000.

FIELD OF THE INVENTION

The present invention relates to a rear projection screen, moreparticularly to large sized rear projection screen.

BACK GROUND OF THE INVENTION

The existing rear projection screen of prior art includes a Fresnel lensfor collecting the image incident light, and a cylindrical lens arrayfor receiving the image light collected by the said Fresnel lens, anambient light absorbing portion and a image light effluence portionformed at the image-light exit side. As to the small sized screen forrear projection TV set, the cylindrical lens array in the screen can bemanufactured by the integrated mold due to the size of the mold issmall. But for the larger sized rear projection screen, such as morethan 150 inches, if the cylindrical lens array in the screen still ismade by the integrated mold, then the cost for the mold will be veryhigh, that is, it is infeasible in view of economic point. Therefore, alarge sized rear projection screen is normally formed by assembling aplurality of small rear projection screen. For example, a patent No. JP1998-260478 disclosed an assembled large sized rear projection screen,which includes a plurality of unit screen in the horizontal andlongitudinal direction, the sidepiece of each unit screen are fixed withthe shade at the back side by screws. The screws are positioned at theinner side of the sidepiece of each unit screen instead of at the seambetween two adjacent unit screens, result that the adjacent unit screenscan be joint tightly almost without black strip shade lights. But thereare still lots of image shading black spots at the position where thescrews are fixed at the sidepiece of each unit screen, and the size ofthe image shading black spots are much larger than the ones of thepixels which form images. Accordingly the integrity and continuity ofimages are damaged.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a large sized rearprojection screen, wherein there is not any shade for the imagesprojected from rear, accordingly to provide with complete images withoutany defects.

The object of the present invention can be realized by the followinglarge sized rear projection screen, which includes:

a Fresnel lens for collecting the image incident light, a cylindricallens array for receiving the image light collected by the said Fresnellens, and an ambient light absorbing portion and a image light effluenceportion formed at the image-light exit side;

wherein the said cylindrical lens array comprises of a plurality ofcylindrical lens elements, these cylindrical lens elements are separatedfrom each other, that is independent, and in parallel, and arrangedclosely between adjacent cylindrical lens element, so that there are noluminous flux loss therebetween. A strengthening area, which is providedwith a rigid reinforced member connecting with cylindrical lens elementson two sides thereof, is formed on the area being from their contactportion to the image-light exist-side surface between adjacentcylindrical lens elements. An ambient light absorbing portion is formedon the image-light exit side in the strengthening area.

With respect to the large sized rear projection screen with the abovementioned structure, as a strengthening area is formed in thecylindrical lens array which is made as outer side of the screen andreinforced members are formed within the strengthening area, so theimpact strength, bending strength and rigidity of the full screen areimproved, and the cylindrical lens will not deformed. In addition, sincethe said strengthening area is located in the area where no luminousflux loss is generated, and the strengthening area dose not shade anylight projected from rear side, the images shown on the full screenpossess the integrity and continuity without shadow or black spotscaused by fixing screws of those prior art And the large sized rearprojection screen of the present invention furthermore dose not have thewide striped shadows which possessed by the market available large sizedscreen assembled by multi-screen unit with sidepieces. As allstrengthening area are located in the area where no luminous flux lossis generated and all strengthening area are provided with ambient lightabsorbing portion, so the ambient light absorbing portion of thecomplete screen according to this invention, i.e. the portion of theblack grounding, is much higher than the ones of the conventional rearprojection screen. Furthermore, due to the cylindrical lens array of thescreen of present invention consist of a plurality of elements, i.e.breaking up the whole into parts, the process of manufacture is simple,the expensive huge mold for the conventional integrated rear projectionscreen is not required according to this invention.

In the said rear projection screen, each cylindrical lens elements canbe formed by many integrated basic cylindrical lenses whose axial planekeep in parallel.

As to the large sized rear projection screen, since each cylindricallens elements possesses many integrated basic cylindrical lenses, thenumber of the element decreases, the efficiency of assembling increases,the production cost of the screen can be reduced while the opticalperformance is not lost

In the said rear projection screen, each cylindrical lens elements maycomprises single basic cylindrical lens.

As to the large sized rear projection screen of this invention, eachcylindrical lens element is formed by many integrated basic cylindricallenses, so that strengthening area can be formed between the singlebasic cylindrical lenses with rigid reinforced members provided therein,accordingly the rigidity of the whole screen is improved. In addition,the ambient light absorbing portions which are provided between basiccylindrical lenses are made of the same material, so the effect of lightabsorbing in the whole screen may remain consistent

In the rear projection screen of this invention, those cylindrical lenselements can be assembled with two kinds of cylindrical lens elements.The first kind of cylindrical lens elements are formed by manyintegrated basic cylindrical lenses whose axial plane keep in parallel,the second kind of cylindrical lens elements are formed by single basiccylindrical lenses.

In the rear projection screen of this invention, the first and secondkind of cylindrical lens elements can be arranged in the manner that oneor more first kind of cylindrical lens element(s) is/ are providedbetween two the second kind of cylindrical lens elements.

In the rear projection screen of this invention, the first and secondkind of cylindrical lens elements can be arranged in the manner that oneor more the second kind of cylindrical lens element(s) is/ are providedbetween two the first kind of cylindrical lens elements.

In the rear projection screen of this invention, the rigid reinforcedmembers can be the shape of “Y” or “T”, wherein the two front wings arepositioned at the image-light exit side. The screen is provided with aouter frame which is connected with the two ends of the reinforcedmembers.

In the rear projection screen of this invention, the cross section ofthe reinforced members can be of polygonal wherein one of anglesprotrudes toward the direction of image-light exiting.

As to the large sized rear projection screen of this invention, sincethe front portion of the reinforced members projects toward out side,the contact between the cylindrical lenses and environmental objects canbe avoided to prevent the cylindrical lens from abrading and damaging.

In the rear projection screen of this invention, the reinforced memberscan be made from rigid materials. At the out side of the reinforcedmembers, i.e. the image-light exit side, a black oxide layer or blackovercoating layer is provided.

In the rear projection screen of this invention, the rigid material canbe metal, carbon fiber or non-metal material with high rigidity, whereinthe metal can be light metal, for example aluminum alloy.

If the reinforced members adopt aluminum alloy, the weight of the screencan be reduced with sufficient mechanical strength ensured.

The reinforced members and the corresponding cylindrical lenses of bothsides can be jointed by engaging a tenon with a mortice.

As to the large sized rear projection screen of this invention, thecontacting area between the reinforced members and the adjacentcylindrical lens elements can be enlarged to ensure the sufficient jointstrength therebetween and to increase the surface area of the ambientlight absorbing portion.

The reinforced members and the corresponding cylindrical lenses of bothsides can be jointed by bond.

The ambient light absorbing portion in the strengthening area can beformed by black reinforced members themselves which absorb the ambientlight.

As to the large sized rear projection screen of this invention, sincethe reinforced members themselves can be light absorbed black parts,then it may function the rigidity improving and ambient light absorbingto simplify the process of screen manufacturing. Furthermore, unlike theambient light absorbing portion of those conventional screen with stuckblack band or coated black layer, light absorbing effect of the ambientlight absorbing portion of this invention will not be easily reduced byabrading or damaging.

The ambient light absorbing portion of the strengthening area can bemade from light absorbing packing which stuff the area.

The Fresnel lens of this invention is made of two overlapped lenses withstraight Fresnel stripes, and the direction of the straight Fresnelstripes of the two lenses keep at right angles each other.

The large sized rear projection screen of this invention facilitates themanufacturing of the Fresnel lens to reduce the relevant productioncost.

The ambient light absorbing portions are also provided at the sidesadjacent to cylindrical lens elements of both sides in the strengtheningarea.

As to the large sized rear projection screen of this invention, theambient light absorbing portions are also provided at the other sidesexcept the front side, i.e. the image-light exit side, so that thediffusion lights which are projected into the inner of the cylindricallens through image light diffused transmission part of the cylindricallens can be massively absorbed, accordingly the portion of the blackgrounding of the complete screen is increased substantially.

The large sized rear projection screen of this invention can be used onthe large screen in TV studio, air port and train stations, the largesized active image advertising in main streets, the large sized imagemonitoring system of industrial control (such as power plant, steelworksand chemical plant), monitoring system of military commanding, analogcampaign system, auditorium, meeting room, the large sized screen inmulti-functional hall, teaching room, entertainment place, and cinemaetc.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective illustrated an embodiment of the large sizedrear projection screen according to the present invention.

FIG. 2 is a perspective illustrated the cylindrical lens array of thescreen shown in FIG. 1.

FIG. 3 is a section view of the cylindrical lens array shown in FIG. 2.

FIG. 4 is a perspective of basic cylindrical lens of the cylindricallens array shown in FIG. 3.

FIG. 5 is a section view of the basic cylindrical lens shown in FIG. 4.

FIG. 6 is a perspective of the reinforced member of the cylindrical lensarray shown in FIG. 3.

FIG. 7 is a section view of the reinforced member shown in FIG. 6.

FIG. 8 is a perspective of another embodiment of cylindrical lens arraywhich constitute the large sized rear projection screen of thisinvention.

FIG. 9 is a perspective of the cylindrical lens elements whichconstitute the cylindrical lens array shown in FIG. 8.

FIG. 10 is a section view of the cylindrical lens elements shown in FIG.9.

FIG. 11 is a schematic of the sides of the reinforced member which canabsorb ambient lights.

FIG. 12 is a perspective view of an alternative embodiment of thecylindrical lens array, showing the reinforced member in the shape of a“Y,” of the screen shown in FIG. 1.

FIG. 13 is a cross-sectional view of the cylindrical lens array shown inFIG. 12.

FIG. 14 is a perspective view of the reinforced member of thecylindrical lens array shown in FIG. 12.

FIG. 15 is a cross-sectional view of the reinforced member shown in FIG.14.

FIG. 16 is a perspective view of the alternative embodiment of thecylindrical lens array shown in FIG. 8, but showing the reinforcedmember in the shape of a “Y.”

FIG. 17 is a perspective view of the cylindrical lens elements whichconstitute the cylindrical lens array shown in FIG. 16.

FIG. 18 is a cross-sectional view of the cylindrical lens elements shownin FIG. 17.

FIG. 19 is a perspective view of another alternative embodiment of thecylindrical lens array, showing the reinforced member in the shape of a“T,” of the screen shown in FIG. 1.

FIG. 20 is a cross-sectional view of the cylindrical lens array shown inFIG. 19.

FIG. 21 is a perspective view of the reinforced member of thecylindrical lens array shown in FIG. 19.

FIG. 22 is a cross-sectional view of the reinforced member shown in FIG.21.

FIG. 23 is a perspective view of the alternative embodiment of thecylindrical lens array shown in FIG. 8, but showing the reinforcedmember in the shape of a

FIG. 24 is a perspective view of the cylindrical lens elements whichconstitute the cylindrical lens array shown in FIG. 23.

FIG. 25 is a cross-sectional view of the cylindrical lens elements shownin FIG. 24.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE PRESENT INVENTION

FIG. 1, which is an embodiment of the large sized rear projection screenaccording to the present invention, the screen includes a Fresnel lens 4for collecting the image incident light, and a Fresnel lens 3 forcollecting the light from Fresnel lens 4, the Fresnel lens 3 and 4overlap each other, and the direction of the corresponding straightFresnel stripes 8 and 9 of the two lenses 3 and 4 keep at right angleseach other. In addition the screen also includes a cylindrical lensarray 2 for receiving the image light collected by the said Fresnellenses, and ambient light absorbing portions and image light diffusedtransmission part are formed at the exit side.

As shown in FIGS. 1-3, the cylindrical lens array 2 consist of aplurality of cylindrical lens elements 5, each cylindrical lens elements5 is formed by only one basic cylindrical lens. As shown in FIGS. 3 and4, image light diffused transmission part 7 is formed at the image lightexit side, the adjacent basic cylindrical lenses 5 keep in parallel andare arranged closely, so that there are no luminous flux loss on theimage incident light therebetween. The strengthening area are formed inthe space of the sides of the adjacent basic cylindrical lenses 5 forthe purpose of improving the mechanical strength of the screen, such asbending strength, impact strength etc., and the strengthening area doesnot shade the image incident light.

As shown in FIGS. 6 and 7, a rigid reinforced member 6 is provided ineach strengthening area, for example the rigid reinforced member can beof batten of aluminum alloy, and the cross section of each batten shapedrigid reinforced member 6 take the shape of polygon, which includes twoinclined planes 6 c and 6 d positioned at the front part (i.e. outside),two inclined side planes 6 a and 6 b, a back plane 6 e positioned at theback side, and several concave portions 10 provided in the two inclinedside planes 6 a and 6 b, wherein a black oxide layer or blackovercoating layer is formed on the said inclined planes 6 c and 6 d andthe inclined side planes 6 a and 6 b to absorb ambient light. Withrespect to the screen with the small sized basic cylindrical lenses, theconcave portions 10 cause the surface of the inclined side planes 6 aand 6 b to be rough. Therefore the friction force and the bonding areaare enlarged with respect to the super large sized screen, the geometrysize of the basic cylindrical lenses are large, so protruding can bemade on the corresponding side face of the adjacent basic cylindricallenses, accordingly the structure of engaging tenon with mortice can beformed during assembling to ensure a tight joint between both parts. Ablack bond can be filled into the concave 10, according to the saidstructure, the reinforced member 6 can absorb ambient light and theeffect of improving mechanical strength of the screen can be achieved.At the same time, the image light from the Fresnel lens will not beshaded, to provide the image shown by the screen with integrity andcontinuity.

As shown in FIGS. 8, 9 and 10, as another embodiment of large sized rearprojection screen according to the present invention, the cylindricallens array of the screen consists of a plurality of cylindrical lenselement 1, the adjacent cylindrical lens elements 1 keep in parallel andare arranged closely. Therefore, there are no luminous flux losstherebetween. A strengthening area is provided therebetween, and thestrengthening area is formed by reinforced member 6 as shown in FIGS. 6and 7, each reinforced member 6 can connect the adjacent cylindricallens elements 1 by bond. Each cylindrical lens elements 1 is formed bymulti integrated basic cylindrical lens 12. Image light diffusedtransmission part 11 is provided at the light transmission side of eachbasic cylindrical lens 12, and ambient light absorbing portions 13 areprovided between the image light diffused transmission parts 11 of theadjacent basic cylindrical lenses 12. The cylindrical lens array in thisembodiment can replace the one of the screen shown in FIG. 1 and 2 toform a rear projection screen together with two overlapped Fresnellenses 3 and 4 at the back side.

As shown in FIG. 11, a rigid reinforced member 6 is provided to connectwith the both sides of the independent basic cylindrical lens 5 of thecylindrical lens element shown in FIG. 2. A plurality of concaveportions 10 are formed in the two inclined side planes 6 a and 6 b ofthe rigid reinforced member 6. A black light absorbing layer is formedon two inclined planes 6 c and 6 d and the two inclined side planes 6 aand 6 b. So with respect to the out side of the single basic cylindricallens 5, a part of ambient light firstly is absorbed by the frontinclined plane 6 c and 6 d, the other part of the light then is absorbedby the corresponding inclined side planes 6 a and 6 b at the both sidesafter it pass through the front diffused transmission part of the basiccylindrical lens 5.

While preferred embodiments of the present invention have beendisclosed, it will be appreciated that it is not limited thereto but maybe otherwise embodied within the scope of the following claims.

I claim:
 1. A kind of rear projection screen, which includes: A Fresnellens for collecting the image incident light; A cylindrical lens arrayfor receiving the image light collected by the said Fresnel lens, and anambient light absorbing portion and image light diffused transmissionpart formed at the image-light exit side; Wherein the said cylindricallens array comprises a plurality of cylindrical lens elements, thesecylindrical lens elements are in parallel and separated from each other,that is independent, and the adjacent cylindrical lens elements arearranged closely, so that there are no luminous flux loss therebetween;a strengthening area, which is provided with a rigid reinforced memberconnecting with cylindrical lens elements on two sides thereof, isformed on the area being from their contact portion to the image-lightexit-side surface between adjacent cylindrical lens elements; an ambientlight absorbing portion is formed on the image-light exit side in thestrengthening area.
 2. The screen of claim 1 wherein the said eachcylindrical lens elements can be formed by a plurality of integratedbasic cylindrical lenses whose axial plane keep in parallel.
 3. Thescreen of claim 1 wherein the said each cylindrical lens elements can beformed by a single basic cylindrical lens.
 4. The screen of claim 3wherein the ambient light absorbing portions are provided at the sidesadjacent to cylindrical lens elements of both sides in the strengtheningarea.
 5. The screen of claim 1 wherein the said cylindrical lenselements can be assembled with two kinds of cylindrical lens elements,the first kind of cylindrical lens elements are formed by manyintegrated basic cylindrical lenses whose axial plane keep in parallel,the second kind of cylindrical lens elements are formed by single basiccylindrical lens.
 6. The screen of claim 5 wherein the said first andsecond kind of cylindrical lens elements can be arranged in a mannerthat one or more second kind of cylindrical lens element(s) is/areprovided between two first kind of cylindrical lens elements.
 7. Thescreen of claim 5 wherein the said first and second kind of cylindricallens elements can be arranged in a manner that one or more the firstkind of cylindrical lens element(s) is/are provided between two secondkind of cylindrical lens elements.
 8. The screen of claim 1 wherein thesaid rigid reinforced members can be the shape of “Y” or “T”, whereintwo front wings are positioned at the image-light exit side, and thescreen is provided with a outer frame which is connected with the twoends of the reinforced members.
 9. The screen of claim 1 wherein thecross section of the said reinforced members can be of polygonal whereinone of angles protrudes toward the direction of image-light exiting. 10.The screen of claim 1 wherein the said reinforced members can be madefrom rigid materials, at the image-light exit side, a black oxide layeror black overcoating layer is provided.
 11. The screen of claim 10wherein the said rigid material can be metal, carbon fiber or non-metalmaterial with high rigidity.
 12. The screen of claim 1 wherein the saidreinforced members and the corresponding cylindrical lenses of bothsides can be jointed by engaging a tenon with a mortice.
 13. The screenof claim 1 wherein the said reinforced members and the correspondingcylindrical lenses of both sides can be jointed by bond.
 14. The screenof claim 1 wherein the said ambient light absorbing portion in thestrengthening area can be formed by black reinforced members themselveswhich absorb the ambient light.
 15. The screen of claim 1 wherein thesaid ambient light absorbing portion of the strengthening area can bemade from light absorbing packing which stuff the area.
 16. The screenof claim 1 wherein the said Fresnel lens is made of two overlappedlenses with straight Fresnel stripes, and the extending direction of thestraight Fresnel stripes of the two lenses keep at right angles eachother.